Adding a resource to a node

This recipe will introduce the language and show you the basics of writing Puppet code. A beginner may wish to reference Puppet 3: Beginner's Guide, John Arundel, Packt Publishing in addition to this section. Puppet code files are called manifests; manifests declare resources. A resource in Puppet may be a type, class, or node. A type is something like a file or package or anything that has a type declared in the language. The current list of standard types is available on puppetlabs website at https://docs.puppetlabs.com/references/latest/type.html. I find myself referencing this site very often. You may define your own types, either using a mechanism, similar to a subroutine, named defined types, or you can extend the language using a custom type. Types are the heart of the language; they describe the things that make up a node (node is the word Puppet uses for client computers/devices). Puppet uses resources to describe the state of a node; for example, we will declare the following package resource for a node using a site manifest (site.pp).

How to do it...

Create a site.pp file and place the following code in it:

  node default {
    package { 'httpd':
      ensure => 'installed'
    }
  }

Tip

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

How it works...

This manifest will ensure that any node, on which this manifest is applied, will install a package called 'httpd'. The default keyword is a wildcard to Puppet; it applies anything within the node default definition to any node. When Puppet applies the manifest to a node, it uses a Resource Abstraction Layer (RAL) to translate the package type into the package management system of the target node. What this means is that we can use the same manifest to install the httpd package on any system for which Puppet has a Provider for the package type. Providers are the pieces of code that do the real work of applying a manifest. When the previous code is applied to a node running on a YUM-based distribution, the YUM provider will be used to install the httpd RPM packages. When the same code is applied to a node running on an APT-based distribution, the APT provider will be used to install the httpd DEB package (which may not exist, most debian-based systems call this package apache2; we'll deal with this sort of naming problem later).